/**
  ******************************************************************************
  * @file           : Base64.cpp
  * @author         : livio[yuanfeng1897@outlook.com]
  * @brief          : base64 encode & decode
  * @attention      : None
  * @date           : 2023/3/2
  ******************************************************************************
  */



#include "Base64.h"
#include <cstdio>

/* BASE 64 encode table */
static const char base64en[] = {
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
        'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
        'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
        'w', 'x', 'y', 'z', '0', '1', '2', '3',
        '4', '5', '6', '7', '8', '9', '+', '/',
};

#define BASE64_PAD      '='
#define BASE64DE_FIRST  '+'
#define BASE64DE_LAST   'z'
/* ASCII order for BASE 64 decode, -1 in unused character */
static const signed char base64de[] = {
        /* '+', ',', '-', '.', '/', '0', '1', '2', */
        62, -1, -1, -1, 63, 52, 53, 54,

        /* '3', '4', '5', '6', '7', '8', '9', ':', */
        55, 56, 57, 58, 59, 60, 61, -1,

        /* ';', '<', '=', '>', '?', '@', 'A', 'B', */
        -1, -1, -1, -1, -1, -1, 0, 1,

        /* 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', */
        2, 3, 4, 5, 6, 7, 8, 9,

        /* 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', */
        10, 11, 12, 13, 14, 15, 16, 17,

        /* 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', */
        18, 19, 20, 21, 22, 23, 24, 25,

        /* '[', '\', ']', '^', '_', '`', 'a', 'b', */
        -1, -1, -1, -1, -1, -1, 26, 27,

        /* 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', */
        28, 29, 30, 31, 32, 33, 34, 35,

        /* 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', */
        36, 37, 38, 39, 40, 41, 42, 43,

        /* 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', */
        44, 45, 46, 47, 48, 49, 50, 51,
};

int base64_encode(const unsigned char *in, unsigned int inlen, char *out) {
    unsigned int i = 0, j = 0;

    for (; i < inlen; i++) {
        int s = i % 3;

        switch (s) {
            case 0:
                out[j++] = base64en[(in[i] >> 2) & 0x3F];
                continue;
            case 1:
                out[j++] = base64en[((in[i - 1] & 0x3) << 4) + ((in[i] >> 4) & 0xF)];
                continue;
            case 2:
                out[j++] = base64en[((in[i - 1] & 0xF) << 2) + ((in[i] >> 6) & 0x3)];
                out[j++] = base64en[in[i] & 0x3F];
        }
    }

    /* move back */
    i -= 1;

    /* check the last and add padding */
    if ((i % 3) == 0) {
        out[j++] = base64en[(in[i] & 0x3) << 4];
        out[j++] = BASE64_PAD;
        out[j++] = BASE64_PAD;
    } else if ((i % 3) == 1) {
        out[j++] = base64en[(in[i] & 0xF) << 2];
        out[j++] = BASE64_PAD;
    }

    return j;
}

int base64_decode(const char *in, unsigned int inlen, unsigned char *out) {
    unsigned int i = 0, j = 0;

    for (; i < inlen; i++) {
        int c;
        int s = i % 4;

        if (in[i] == '=')
            return j;

        if (in[i] < BASE64DE_FIRST || in[i] > BASE64DE_LAST ||
            (c = base64de[in[i] - BASE64DE_FIRST]) == -1)
            return -1;

        switch (s) {
            case 0:
                out[j] = ((unsigned int) c << 2) & 0xFF;
                continue;
            case 1:
                out[j++] += ((unsigned int) c >> 4) & 0x3;

                /* if not last char with padding */
                if (i < (inlen - 3) || in[inlen - 2] != '=')
                    out[j] = ((unsigned int) c & 0xF) << 4;
                continue;
            case 2:
                out[j++] += ((unsigned int) c >> 2) & 0xF;

                /* if not last char with padding */
                if (i < (inlen - 2) || in[inlen - 1] != '=')
                    out[j] = ((unsigned int) c & 0x3) << 6;
                continue;
            case 3:
                out[j++] += (unsigned char) c;
        }
    }

    return j;
}
